Effect of cobalt loading on the solid state properties and ethyl acetate oxidation performance of cobalt-cerium mixed oxides

Abstract

Cobalt-cerium mixed oxides were prepared by the wet impregnation method and evaluated for volatile organic compounds (VOCs) abatement, using ethyl acetate (EtAc) as model molecule. The impact of Co content on the physicochemical characteristics of catalysts and EtAc conversion was investigated. The materials were characterized by various techniques, including N₂ adsorption at -196°C, scanning electron microscopy (SEM), X-ray diffraction (XRD), H₂-temperature programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS) to reveal the structure-activity relationship. The obtained results showed the superiority of mixed oxides compared to bare CeO₂ and Co₃O₄, demonstrating a synergistic effect. The optimum oxidation performance was achieved with the sample containing 20wt.% Co (Co/Ce atomic ratio of ca. 0.75), in which complete conversion of EtAc was attained at 260°C. In contrast, temperatures above 300°C were required to achieve 100% conversion over the single oxides. Notably, a strong relationship between both the: (i) relative population, and (ii) facile reduction of lattice oxygen with the ethyl acetate oxidation activity was found, highlighting the key role of loosely bound oxygen species on VOCs oxidation. A synergistic Co-Ce interaction can be accounted for the enhanced reducibility of mixed oxides, linked with the increased mobility of lattice oxygen.

Keywords: CeO(2); Co(3)O(4); Cobalt (Co)-based catalysts; Ethyl acetate oxidation; Volatile organic compounds (VOCs).